Effect of baseplate flexibility and rail pad stiffness on slab track dynamics

The dynamic properties of the rail fastening system play a significant role in the dynamic performance of railway tracks and their noise emission. The aim of this work is to conduct a comprehensive study of the vibrational behaviour of a resilient baseplate and to evaluate its influence on the dynamics of the slab track system in the frequency range relevant to noise radiation. The frequency responses and mode shapes of a baseplate have been measured in the laboratory, both when freely supported and when attached to a rigid base, and a corresponding finite element model has been developed and verified. A dynamic model of the slab track allowing for the flexible behaviour of the baseplate is developed by coupling the finite element model of the baseplate with a 2.5D wavenumber finite element model of a rail. The frequency-dependent dynamic stiffness of three different rail pads used in this baseplate has also been measured using the indirect method and approximated using a simple function. The developed track model gives good agreement with the measurements in terms of the driving point mobility, track decay rate and average transmissibility. Inclusion of the baseplate flexibility is important for achieving good agreement; nevertheless, the vibration modes of the baseplate do not feature strongly in the results. The rail pad stiffness has a strong effect on the point mobility and track decay rate above 1 kHz. However, inclusion of the frequency-dependent stiffness of the rail pad has only a small effect on the results. • Model of slab track vibration allowing for the flexible behaviour of the baseplate. • Model and measurements of frequency response and mode shapes of a rail baseplate. • Frequency-dependent stiffness of three different rail pads has been measured. • The baseplate flexibility has an important effect on the vibration of a slab track. • Effect of rail pad stiffness on mobility and track decay rate of slab track shown.